1. Field of the Invention
This invention relates to tools for grasping objects, and more particularly, to a cordless vacuum wand used to grasp silicon wafers during the manufacture of integrated circuits.
2. History of the Prior Art
Integrated circuits are manufactured on thin silicon wafers which are circular in shape and range in diameter from four to twelve inches. The wafers undergo many different processes during the overall manufacturing cycle, and each process may be performed by a different machine. It is critically important during the entire cycle that the wafers be kept as clean as possible, and that they be handled as carefully as possible to avoid damaging the integrated circuits thereon. Therefore, wafers must be transported with the utmost care from machine to machine within a clean-room manufacturing facility.
Much of the transporting of wafers during the manufacturing process is performed by automated transporters. Robotic arms remove the wafers from each processing machine and place them in a transportation rack. The rack is moved to the next processing machine where another robotic arm removes the wafers from the rack and places them in the machine. Generally, if all components maintain proper alignment in the wafer-transportation system, the entire cycle can be handled automatically. Sometimes, however, it is necessary for human intervention and, therefore, the manual grasping and transportation of wafers.
The most commonly used means for grasping and transporting wafers is with a vacuum wand. FIG. 1 is an illustration of a cut-away portion of a typical wall-mounted, factory-installation of high vacuum tubing and vacuum wands. High vacuum tubing 10 is installed on a wall 11 between a central vacuum pump (not shown) and the area of the manufacturing facility where wafers are most commonly handled. Individual vacuum lines, known as umbilical cords 12, branch off of the high vacuum tubing 10 every few feet, and are equipped with wands 13 at the ends. Each wand 13 has a switch 14 for turning on the suction of the vacuum, and is equipped with a broad, flat tip 15. The flat tip 15 has a depressed central region 16 where the suction from the vacuum is applied. When the flat tip 15 is placed against the flat surface of a silicon wafer, a partial vacuum is created in the area of the depression 16, and the suction force holds the wafer securely against the tip of the vacuum wand. In this manner, the wafer may be handled with minimal stress applied to the wafer, and without touching the wafer with hands or gloves which could contaminate the integrated circuits thereon. This set-up works acceptably well as long as wafers do not need to be transported beyond the range of the umbilical vacuum cord 12.
A major problem arises, however, when wafers must be carried beyond the range of the umbilical cord 12, or in areas of the manufacturing facility where high vacuum tubing 10 has not been installed. The installation of high vacuum tubing is very expensive, costing approximately $40,000 to $50,000 to install in a new area of a factory. Therefore, high vacuum tubing is generally not run to all areas. In those areas, other means must be utilized to handle wafers.
In the past, one such means has been to use tweezers. Tweezers, however, pose several problems and may potentially damage wafers being handled and the integrated circuits thereon. Tweezers can cause stress fractures in the silicon, depending on how hard the wafer is squeezed. The fractures may not be discernable until much later in the manufacturing process when considerable time and expense has been invested, and faulty integrated circuits are detected. Tweezers may also scratch the wafer or even chip the edge if it is hit with sufficient force. Chipped edges may cause further contamination of the wafer or other wafers from silicon dust which is produced from the break.
It would be a distinct advantage to have a relatively inexpensive device for safely handling wafers in areas of a manufacturing facility which do not have high vacuum tubing installed. The device of the present invention provides such a device.